how to fix P0420 code in my Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the pre-cat and post-cat oxygen sensors in the exhaust system.
2. Disconnect the wiring harness: Gently pull the connector from the sensor.
3. Remove the sensors: Use an oxygen sensor socket to unscrew the sensors from the exhaust manifold and catalytic converter.
4. Install new sensors: Apply anti-seize compound to the threads of the new sensors and install them, tightening to manufacturer's torque specifications (typically 30 lb-ft).
5. Reconnect the wiring harness: Ensure the connections are secure.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Check for physical damage: Look for dents, rust, or signs of overheating.
2. Remove the catalytic converter: Unbolt the mounting brackets and exhaust flanges using a socket set.
3. Inspect for clogs: Shine a light through the converter; if the flow is restricted, it needs replacement.
4. Install the new catalytic converter: Position it in place and secure it with bolts, tightening to specifications (typically 40 lb-ft).
5. Reattach any heat shields or components removed during the process.

4. Clear Codes and Test Drive

1. Reconnect the battery: Attach the negative terminal back.
2. Use the OBD-II scanner: Clear the P0420 code from the ECM.
3. Test drive the vehicle: Drive for a minimum of 20 miles to allow the system to recalibrate and monitor for any reoccurring codes.